Abstract

Since typically low temperatures turn the quasi three level system of Yb:YAG into a four level system much higher efficiencies are expected by cryogenic cooling. Former experiments achieved efficiencies up to 30 % [3], which is below theoretical expectations [1,2]. To increase the efficiency through a better overlap between the pumped area and the seed beam profile, a novel all-reflective relay imaging amplifier has been built. Astigmatism compensation of the setup was achieved by folding the beam pass out of plane. The Yb:YAG crystal was placed in a liqiud nitrogen cooled mount inside a vaccum chamber.

© 2011 Optical Society of America